[Driver] Don't use capture for InstalledDir

This is another attempt to address the issue introduced in
ae8b2cab67.

We cannot capture InstalledDir because FileCheck doesn't handle
the backslashes correctly, so instead we just consume the entire
path prefix which is what other tests are doing.

clang/test/Driver/darwin-ld.c

@@ -368,5 +368,4 @@
 
 // RUN: %clang -target x86_64-apple-darwin10 -### %t.o 2> %t.log
 // RUN: FileCheck -check-prefix=INSTALL-DIR %s < %t.log
-// INSTALL-DIR: InstalledDir: [[INSTALLDIR:.+$]]
-// INSTALL-DIR: "-L[[INSTALLDIR]]{{/|\\\\}}..{{/|\\\\}}lib"
+// INSTALL-DIR: "-L{{.*}}{{/|\\\\}}..{{/|\\\\}}lib"